The movement against the poll tax was one of the most remarkable in modern Britain. Its most famous event took place 20 years ago this week when around 200,000 people marched in London, only to be met by police violence in Whitehall as they neared their rally in Trafalgar Square.

By the end of the day, hundreds were injured and arrested, South Africa House (symbol of the hated apartheid) had been under attack, portacabins on building works set on fire, and shops and cars wrecked as rioting continued throughout Soho and the West End.

While denunciations of riots and violence came from right and left of the political spectrum, that day marked the beginning of the end for the hated tax.

The months of non payment which followed put the nail in its coffin – and finished its architect, Margaret Thatcher, who was forced out of office by the end of the year.

The Tories introduced the poll tax as a replacement for the rates, as local taxes were known. These were based on the value of property and, while they had all sorts of anomalies, in general the richer the house or area, the more rates were paid.

The Tories tried to change all this, partly to modernise local government financing, but partly in response to long held Tory prejudice that the rates in some way discriminated against their natural supporters.

The idea was very simple: that local tax should be paid per head, not by property. In the words of Thatcher’s sidekick, Nicholas Ridley, the same would be paid by ‘the duke and the dustman’.

It seems incredible now that they thought they could get away with it, but Thatcher’s hubris was at its height in the years after defeating the miners and the printers.

The tax was introduced in Scotland in 1989, a year before England and Wales. That should have been a warning: a mass campaign was built, led by Tommy Sheridan who went on to found the Scottish Socialist Party.

In working class areas there was mass opposition, as people rightly saw the tax burden being pushed more heavily onto the working class. Working class families with adult children living at home were particularly hard hit, often finding the amount they had to pay trebling or quadrupling.

But even couples were finding their local taxes doubling overnight, while people living in big houses saved thousands of pounds over the old rates.

It was met with mass opposition throughout the country. In London, huge demonstrations outside town halls sometimes turned to riots.

In Hackney, rioting led to the (selective) smashing of windows: every estate agent lost their windows. Everywhere there were protests and pledges not to pay the poll tax.

So the atmosphere was feverish when the mass demonstration set off from Kennington Common to Trafalgar Square on 31st March. But the large crowd was peaceful until attacked by police when it sat down in Whitehall.

That attack was ferocious, leading to broken limbs on the part of protesters and to sheer terror among those in the crowd with children.

The fighting went on for hours, the police pushing their assault through Trafalgar Square and then continuing it in the narrow streets north of the square (something no one could remember happening before).

As the march reached Trafalgar Square, the police attacked it. A huge battle ensued and a riot spread through central London.

Cars were burnt outside the English National Opera in St Martins Lane, jewellers windows were broken in Regent Street and, back in Trafalgar Square the crowd tried to set fire to South Africa’s Embassy. When they failed another building on the south side of the Square was set ablaze.

As the struggle with the police reached its peak a handmade banner reading ‘Yorkshire Miners Against the Poll Tax’ could be seen heading into the thick of the struggle.

The Labour party officially had played no part in the mobilisation that day, in fact their line was to pay it and wait for a Labour government to repeal the law! Neil Kinnock now denounced the violence, as he had done over the miners’ strike.

The only organisation which defended what happened was the Socialist Workers party, which had built the demonstration alongside the Socialist Party (Militant).

But no one was now in doubt how serious opposition to the hated tax was. The next day, Thatcher’s Home Secretary David Waddington visited Soho to see the damage and immediately attracted a crowd of angry demonstrators.

More intelligent Tories must have known then that the game was up.

The campaign now moved to non payment as people burnt their poll tax demands and refused to pay a penny. They were summoned to court and contested the summonses. The harassed magistrate I appeared before said he had no choice but to issue a summons but waived any costs of the case.

The local courts were being clogged up and there were often no mechanisms to enforce payment. Some people were imprisoned for non payment, but most could not be enforced and were eventually dropped.

By August of 1990 one in five of the entire population had refused to pay, with figures reaching up to 27 percent of people in London.

Some 20 million people were issued with court summons for non-payment. Many local authorities were faced with a crisis, and councils faced a deficit of £1.7 billion for the next year.

In November 1990 Thatcher was forced out of office. Tory politicians and commentators all claimed this was about internal party divisions, especially about Europe. But it is widely agreed now that the poll tax was key.

To many Tories, the country now seemed ungovernable and they saw her unpopularity as a block to changing that. So even her own party turned on her.

The anti poll tax campaign was Thatcher’s nemesis and the tax was dropped soon afterwards.

‘Can’t pay, won’t pay’ was the essence of the campaign – a slogan we should be getting off the shelf for the battles over cuts and taxes on the horizon.